That's according to the annual report released Friday by Ohio-based Lake Carriers' Association.

U.S.-flag ships working on the Great Lakes carried 89.5 million tons of the dry-bulk cargo last year, which is down 4.6 percent from 2011. The Green Bay Press-Gazette reports it's also down 1.5 percent from the five-year average of 90.8 million tons.

Iron ore shipments dropped 4.3 percent from 2011 but the total was above the five-year average of 42 million tons.

Coal shipments fell to 17.6 million tons last year, below the five-year average of 22.5 million tons.

The decline has been partly attributed to the phasing out of Canadian coal-fired electrical plants.

Cement and limestone shipments were slightly ahead of the five-year average.

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